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<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // 接口地址：https:api.apiopen.top/getJoke

        const p = new Promise((resolve,reject)=>{
            //  1. 创建对象
            const xhr = new XMLHttpRequest()

            // 2. 初始化
            xhr.open("GET","https:api.apiopen.top/getJoke")

            // 3. 发送
            xhr.send()

            // 4.绑定事件，处理响应结果
            xhr.onreadystatechange = function(){
                // 判断
                if(xhr.readyState === 4){
                    // 判断响应码
                    if(xhr.status >= 200 && xhr.status <= 300){
                        // 表示成功
                        resolve(xhr.response)
                    }else{
                        // 如果失败
                        reject(xhr.status)
                    }
                }
            }
        })
        
        // 指定回调
        p.then(function(value){
            console.log(value)
        },function(reason){
            console.error(reason)
        })
    </script>
</body>
</html>